School bus drivers in the largest U.S. public school system, New York City, are on strike for a second day Thursday, leaving more than 150,000 students looking for alternative transportation to get to class.

Eight thousand unionized bus drivers walked off the job on Wednesday, taking to the picket lines to dramatize their demand for job security for drivers in any new contract. Their old contract does not expire until June 30th.

School bus drivers in New York City work for private companies under contract to the city. Mayor Michael Bloomberg maintains that a 2011 court ruling prohibits the city from including job protection in new contracts.

Most of New York City's 1.1 million students walk to school or use mass transit to get there. Those who rely on buses include 54,000 special education students and others who live too far away from schools.

The city is offering free public transit cards for students affected by the strike. Officials say parents will be reimbursed if they need to drive or hire a car to bring their children to school.

No talks are scheduled in the dispute.